The trend in the circuit protection industry is currently toward complete circuit protection which is accomplished by the addition of supplemental protection apparatus to standard overcurrent protective devices, such as molded case circuit breakers. In the past, when such auxiliary protection apparatus or other circuit breaker accessories were combined with a standard circuit breaker, the accessories were usually custom-installed at the point of manufacture. The combined protective device, when later installed in the field, could not be externally accessed for inspection, replacement or repair without destroying the integrity of the circuit breaker interior. An example of one such factory installed circuit breaker accessory is found in U.S. Pat. No. 4,297,663 entitled "Circuit Breaker Accessories Packaged in a Standardized Molded Case", which Patent is incorporated herein for reference purposes.
A more recent example of a circuit breaker including additional accessories is found in U.S. Pat. No. 4,622,444 entitled "Circuit Breaker Housing and Attachment Box" which allows the accessories to be field-installed within the circuit breaker without interfering with the integrity of the circuit breaker internal components. This is accomplished by mounting the accessories within a recess formed in the circuit breaker enclosure cover.
An electronic trip actuator which is mounted within the circuit breaker enclosure is described within U.S. Pat. No. 4,679,019 entitled "Trip Actuator for Molded Case Circuit Breakers". The circuit breaker actuator responds to trip signals generated by an electronic trip unit completely contained within a semi-conductor chip such as that described within U.S. Pat. No. 4,589,052. The development of a combined trip actuator for both overcurrent protection as well as accessory function is found within U.S. Pat. 4,700,161 entitled "Combined Trip Unit and Accessory Module for Electronic Trip Circuit Breakers". The aforementioned U.S. Patents which represent the advanced state of the art of circuit protection devices are incorporated herein for reference purposes.
U.S. Pat. No. 4,806,893 describes a molded case circuit breaker actuator-accessory unit wherein the integrated overcurrent trip actuator and multiple accessory unit containing the control electronics and mechanical interface components are contained on a single structure mounted within a single recess. In some circuit breaker designs the actuator unit and the accessory unit are mounted within separate enclosures. The accessory, for example, could comprise a shunt trip or undervoltage device as described within the aforementioned U.S. Patent.
A recent example of a combined circuit breaker actuator-accessory unit is found within U.S. Pat. No. 4,894,631 entitled "Molded Case Circuit Breaker Actuator-Accessory Unit". The actuator-accessory unit employs several springs for propelling the trip armature and resetting the actuator-accessory levers. The components are carefully selected to result in a predetermined fixed separation gap between the tip of the actuator-accessory armature and the actuator-accessory trip actuator arm to compensate for the accumulative tolerances of the actuator-accessory unit components. A recent example of a means for positioning an armature relative to an electromagnet is found within U.S. Pat. No. 4,825,179.
The instant invention improves over the earlier trip actuator-accessory unit by the provision of a tolerance take-up spring on the actuator-accessory armature tip to precisely set the separation gap between the actuator-accessory armature tip and the actuator-accessory trip actuator arm.